Automatic consistency control means



Nov. 17, 1942. KEHQE r 2,302,327

AUTOMATIC CONSISTENCY CONTROL MEANS Original Filed NOV. 28, 1940 -4Sheets-Sheet 1 F' IG.4.

FIG.I.

INVENTORJ R lab A/(El/as 3 23 awe? WE/L NOV. 17, R D KEHQE HAL AUTOMATIG CONS I S TENCY CONTROL MEANS Original Filed Nov. 28, 1940 4Sheets-Sheet 2 Q N m no N m\ N BY ad, mama? Nov. 17, 1942.

R. D. KEHOE ETAL 2,302,327

AUTOMATIC CONSISTENCY CONTROL MEANS Original Filed Nov. 28, 1940 4Sheets-Sheet 5 FIG. 8

INVENTORS R C/MR) .2 AE/faE @J CUZY' M E/L.

Nov. 17, 1942. R. D. KEHOE Er 2,302,327

AUTOMATIC CONSISTENCY CONTROL MEANS V Original Filed Nov. 28, 1940 4Sheets-Sheet 4 [NVENTORS Patented Nov. 17, 1942 Richard D. Kehoe,Hadlyme, Conn., and Curt Weil, Elmhurst, N.'Y., assignors ,to Paper andIndustrial Appliances, Inc., New York, N. Y., a corporation of New YorkOriginal application November 28, 1940, Serial No. 367,530. Divided andthis application July 25,. 1942, Serial No. 452,330 v 6 Claims.

This is a division of our parent application Serial No. 367,530, filedNovember 28, 1940, disclosing a pulp density control station comprisinga flow box provided with a round-the-end flow baflle whereby the stockis caused to flow through the box or station in a U-shaped path. It isfrom this U-shaped flow that the control impulse for the density controlof the stock by means of diluting water is derived.

The aforementioned .parent application covers the feature that in thiscontrol station the regulation of the pulp density with diluting wateris effected automatically with the aid of a pressure differentialresponsive device that is structurally embodied in and unitary with theround-the-end flow bafile.

The present/divisional application covers a feature also embodied in theround-the-end flow baflle type of flow box or control station, wherebyexcess undiluted or unregulated stock is caused to discharge over aby-pass weir at the entrance of the U-shaped flow path of the stock fromwhich the control impulse proper is derived. By co-ordinating theadjustable height of this excess by-pass overflow weir with therespective adjustable heights of an inlet and an outlet Weir of theaforementioned U-shaped flow path, desired flow conditions may beobtained and maintained therein along that path so that a desireddensity control can be derived therefrom.

Therefore, the following specification and drawings in the presentdivisional application are identical with those of the aforementionedparent application.

This invention relates to apparatus for controlling the stockconsistency of a pulp such as is used for paper making, or of rag stockused in the manufacture of dry felts, or of free sulphite stocks.

Variations in stock consistency cause trouble whenever and wherever theyoccur. It is impossible to attempt manual control of consistency becauseno operator can judge stock consistency accurately. Manual control,aided by consistency testing is also impractical, because no operatorcan make consistency tests with sufficient speed and accuracy and adjustthe amount of diluting water quickly enough to prevent consistencyvariations. Many devices, based on various principles, have been used tocontrol diluting water automatically in an attempt to preventirregularities in operation that result from consistency variations.

The operation of this invention is based on the following principle:

Stock flowing through a trough or channel assumes a natural slope. Theangle of slope -depends 'on the consistency of the stock. The higher theconsistency the steeper the slope. A slope is formed because a certainamount ot'energy isneeded to move the stock through the trough toovercome internal and wall friction. This energy is expressed in theform 01 a pressure heath.

The potential head energy is converted into velocity energy and as thestock moves along, less energy is required. The velocity is acceleratedand as the stock quantity remains the same, and the velocity isincreased, it follows that the'crosssection of the stock must decreaseto allow the.

same amount of stock to pass through the crosssection in the time unit.As the width of the trough remains the same theheight of the stockmustdecrease, thus forming a slope.

This phenomenon-the difference in head pressure between two spacedpoints in a troughis 1 used to actuate a valve, controlling theadmission of diluting water to the stock. Inasmuch as the the characterherein contemplated, convert a* pulp or stock of fluctuating andexcessive viscosity into one of substantially constant viscosity ofdesired dilution by automatically varying the rate of feed of water orother diluent to the stock,

in keeping with the demand of the fluctuations. That is to say, a risein viscosity of the pulp will cause a corresponding increase in thewater fed to the stock, while a drop in viscosity causes a decrease inthe amount of water supplied.

Where such a device operates due to a sloping stock level, ithas beenfound that in a stock beating engine, for instance, the slope of theliquid level is subject to uncontrollable variations, that arecharacteristic of the operation of the beater and result from thechanging resistance which the stock solids offer to the beater roll, andfrom the flow disturbances caused by coarse lumps or aggregations ofsolids or the like.

It is one of the objects of this invention to establish suitable stockflow conditions as a basis for the proper functioning of the viscositycontrol device. Another object is to improve and simplify theconstruction of the control device.

To attain some of these objects, a special viscosity control station ortank is provided and disposed at a Point past the heater and madeindependent of the disturbing influences thereof and of pumps. Thiscontrol station is designed to provide an undisturbed, even, andconstant-volume stock flow as a basis for the viscosity indications andresponses from which the impulses for viscosity control are to bederived. Since the function of the control station is to supply to thestock more or less water, the stock acted upon inthe control stationmust have at least a maximum viscosity and a minimum dilution ultimatelyrequired of it.

Features relating to the control station comprise the arrangement of aflow passage or channel for stock whose viscosity is to be regulated ata favorable point in the stock flow path. The flow through this passageor channel is kept substantially free from undue fluctuations ordisturbances by the provision of a specially arranged feed and outletmeans.

This control station is designed with an inlet or feed section soarranged that unregulated or undiluted stock excessively fed theretobeyond the amount that can have its viscosity regulated overflows and isreturned to a point in the flowpath ahead of the control station. Thisacts somewhat as a safety valve and excess flow absorber so that to theviscosity-controlling section of the station there is admitted asubstantially constant volume of stock into the flow passage forviscosity regulation. The slope of the liquid level between inlet andoutlet of the control station is the basis for the operation of theviscosity control. A controllable discharge opening at the outletsection of the control channel permits the withdrawal of the quantity ofstock of regulated dilution needed for the current production.

Other features have to do with the construction of the viscosity controldevice per se, and with the manner of its mounting in the controlstation.

The mechanical design of the control of this invention consists of twopresssure pipes submerged in the stock at two spaced points suppliedwith compressed air. The back pressure in the two pipes varies accordingto the angle of the slope of the stock. This difierence inpressureactuates an impulse amplifying instrument and controller, which inv turnoperates the motor of the diluting water valve. The instrument isdesigned so that the air pressure regulates the diluting water valve tokeep the differential back pressure in the two pressure pipes the same.In

other words, the angle of the stock slope is kept the same by admittingthe proper amount of diluting water as the consistency changes.

Other features include a flushing water connection for the bubble pipes,and for vertical adjustability of the bubble pipes relative to oneanother.

In one embodiment the flow passage that is part of the control stationis established in a tank by way of a longitudinally extending verticallydisposed round-the-end-flow bafiie so that inlet and outlet are disposedsubstantially at the same end of the tank, the bubble pipes of thecontrol device straddling the baffle.

In a more specific case the bubble pipes are incorporated directly inthe baille wall in such a way as to offer no obstruction to the stockflow and to avoid flow disturbance.

In an embodiment comprising the application to the treating of paperpulp, the control station or box is disposed at a. point in theflowpath, which lies between the beater engine and the refiner, or morespecifically between the stui! chest following the beater and therefiner or Jordan. This is by way of example, since the control stationcan be disposed at other suitable points in the fiowsheet. However, thisembodiment may be modified by placing the control station at otherpoints of the flowpath, for instance, more nearly ahead of the screenthat feeds the paper machine. so long as it is independent of disturbinginfluences normally present in the stock flowpath.

Another feature of this invention resides in the use of a controlleroperated by the differential pressure derived from the bubble pipes,which controller operates a diaphragm type of motor operated valve forsupplying more or less diluting water to the stock. This invention alsoproposes to use a pneumatic-recorder that records or registers on onedisc or tape: (1) the consistency of the stock in the viscosity controlstation, and (2) the consistency of the stock at some point in theflowpath prior thereto. It is common to have such discs marked not onlyby days, for say, six days at a time, but by hours of each day. Thus, asupervisor can, from an inspection of such a recorder disc, observe therecord of action'of the viscosity control station but also compare theperformance of that station with performance of a prior station in theflowpath. If the performance of the viscosity station is indicated ashaving become uneven at some time, and at the same time, unevenoperation is shown of the prior station, then the inspecter is thusinformed that the trouble was at a station ahead of the viscositycontrol instead I of in the control itself.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription. In the following description and in the claims, parts willbe identified by specific names for convenience, but they are intendedto be as generic in their application to similar parts as the art willpermit. In the accompanying drawings there has been illustrated the bestembodiment of the invention known to us, but such embodiment is to beregarded as typical only of many possible embodiments, and the inventionis not to be limited thereto.

The novel features considered characteristic of our invention are setforth with particularity in the appended claims. The invention itself,however, both as to its organization and its method of operation,together with additional objects and advantages thereof, will best beunderstood from the following description of a specific embodiment whenread in connection with the accompanying drawings in which:

Figure 1 shows a longitudinal sectional view of the viscosity orconsistency control tank.

Figure 2 is a perspective view thereof with parts broken away.

. Figure 3 is a vertical transverse sectional view thereof with adiagrammatic showing of the mechanisms associated with the control tank.

Figure 4 is a plan view of the tank.

Figure 5 is an elevational view of the bubblepipe assembly shown in itsposition in the midfeather of the control tank.

Figure 6 is a side view of the apparatus of Figure 5.

Figure 7 is a sectional plan view taken along the line 'I--'! in Fig. 5.b

Figure 8 is a somewhat diagrammatic view of asoaaav a recorder chart ordisc but with actual operating graphs shown thereon.

;. Taking up for description first, the viscosity or consistency controlstation and its details, Ii indicates the control basin or tank thatprovides a flow-through channel or trough, and has a vertical,longitudinally-extending partial partition or mid-feather 12 that leavesa free round-theend passage ii at one end but at the other end there areprovided three adjustable height dams l4, l and "extending between themidieather and the tank walls I1, I I and I9 respectively. indicates theother wall of the tank which may be rounded or bevelled. These dams forma feed inlet compartment 2| and an overflow compartment 42. A stockinlet pipe 23 communicates with inlet compartment 2| and a stock outflowpipe 24 communicates with overflow compartment 22. 25 indicates anoutlet for the regulated and diluted stock, outflow from which iscontrolled by suitable valve mechanism indicated generally by 25. Eachof the adjustable height dams is preferably formed of removable boardsor sections 21 that slide vertically in appropriate aligned grooves 28and 29 respectively on the midi'eather and the tank wall.

A water inlet pipe or conduit 30 has a perforated and enlarged terminussection 3| disposed in the stock-liowpath just after the stock spills orcascades over the dam l4 from the inlet compartmentdl. This pipe 30 hasa valve 32 between lts terminus 3i and a source of dilutin water. Thevalve is controlled, in my preferred embodiment, by a diaphragm motormechani m 33 that is air operated. Disposed adjacent to the midi'eatherl2 on the high stock-slope side of the midfeather is a high head bubblepipe 34 and on the other side of the midfeather. a lower head bubblepipe 35, each having a free outlet or nipple 88 from which air bubblesare emitted into the stock 31. The bubble pipes must be spaced from oneanother in the direction 01' stock flow. Thus these pipes may straddlethe midfeather l2, although my preferred disposition of these pipes isto embed them out of stock flow obstructing position within the contourof the midfeather l2 in a recess 38 therein into which fits a box-likeconstruction or casing 39. A certain amount of vertical slidableadjustment is provided between the bubble pipe outlets or nipa waterpipe II that has a valve 52 controlling it. It will be noted that thethrottling or resistance devices 44 and 50, as well as thereductionvalve 41, and the U-shaped casing 42 are also a mounted uponthe common frame 4lic,"making this control device inclusive of thebubble pipes, the throttling devices and the reduction valve asubstantially self-contained unit.

Referring to Figure 3, from pressure leveling casing 44 there extends abranch pipe 53 from the high head pressure line that leads to and isconnected with a control or regulator instrument 54. Similarly, from thepressure leveling casing there extends a branch pipe from the lower headpressure line that leads also to the control instrument 54. Alsoconnected to the control instrument 54 is an air-pressure line 515, theair in which is controlled by the regulator instrument 54 and thenpasses through pipe 5'! to the diaphragm motor valve operating mechanism33. The control instrument 54 is of the type obtainable in the openmarket and operates when diflerential pressure passes a danger point.That is, when the high head back pressure from bubble pipe 34 isdangerously higher than the pressure in .the lower head back pressurefrom bubble pipe 35, the regulator instrument permits air pressure fromline 53 to pass to and operate the motor controlled valve 32 thatprovides diluting water. For example, the trade name of a satisfactoryinstrument of this type is Stabilog made by The Foxboro Company, ofFoxboro, Massachusetts.

Such an instrument has a recording or registering attachment including arecording chart 6!] that usually has a capacity for a one day record,and the record is divided into hours and minutes. In our preferredembodiment, we use an instrument that has two recording pens or stylusesGI and 62. One stylus makes a graph 53 on the chart 50 that is a recordof the consistency of the regulated stock leaving the control station ortank H, while the other stylus makes agraph 64 on the same chart (andusually more or less concentric therewith) that is a record of theconsistency of the unregulated or undi uted stock entering the viscositycontrol station i l.

The viscosity or consistency control station II and its associated partsis located in a place in a paper-making flowpath where it issubstantially free from pulsations or other variations.

In one preferred form, it is located between the stuff-chest and therefiner, That is, in the complete flowsheet, there would first come thebeating engine, then the stuff-chest, from which the stock is usuallypumped to the control station that passes upwardly to connect with aU-shaned casing 42, then outwardly through valve 43 into a pressureleveling casing or throttling device 44, out from the bottom thereof bypipe 4| leading into a manifold pipe 45 associated with which is apressure gauge 46. Manifold pipe 45 pass s into a knob-operatedpressure-reducing valve 41 which in turn is connected with a sourceofairpressure through pipe 48. Lower head bubble pipe 35 similarly isconnected to a bent or flexible pipe 49 that provides a conduit thatpasses upwardly to connect with the U-shaped casing 42, then outwardlythrough valve 50' into a pressure leveling casing or throttling device50, then out from the bottom thereof by pipe 49' leading into themanifold pipe 45, through the pressure reducing valve 41 to air-supplypipe 48. The U- shaped casing 42 is connected at its top with I I.Following the control station is the refiner or Jordan. Excessunregulated and undiluted stock spills from-the entrance end of thecontrol station and flows back to the stuff-chest, whereas regulated anddiluted stock flows from the control station to the refiner, althoughany excess of this can also be recycled back to the stuff-chest alongwith the excess unregulated stock that is going back there. In anotherarrangement, the control station II and its associatedparts, are locatedbetween the refiner or Jordan station and the screen that is ahead ofthe paper machine.

In the operation of the control station II and its associated parts,stock enters the tank H through the inlet pipe 24 upflowing into theinlet compartment 2|.

stock spills or cascades into the control area of the tank I l. The topplank or, weir of dam I8 is so. adjusted that any unregulated andundiluted stock in inlet compartment 2i that is in excess of thatdesired to enter the main control area of the tank H, is spilled orcascaded over the dam l5 into overflow compartment 22 from whence it isconducted by outlet pipe 24 back to the stuff-chest or other point aheadof the control station. Stock that hasspilled over dam M flows in aU-shaped path around the midfeather l2 through.space i3 and ultimatelyto dam, l6 over which the stock spills or cascades into overflowcompartment 22. Thus excess regulated and diluted stock mixes with theexcess unregulated and undiluted stock in the overflow compartment 22and passes in admixture therewith out through pipe 24 to the stuffchest.Regulated and diluted stock is drawn off from the control stationthrough take-oil opening 25 that is controlled by valve 26. Thisregulated stock then goes to a reflning station or to whatever thesubsequent treatment of it is to be.

Stock in spilling over dam l4 encounters the perforated section 3| ofthe water diluting pipe 30 where and by which the stock is diluted asrequired, due to the control thereof initiated by the differential backpressure set up in the bubble pipes 34 (higher pressure) and 35 (lowerpressure). The difference in back pressures set up in the air-emittingbubble pipes is due to the slope of the fluid level assumed by the stockas it flows from the feed end at dam is to the outlet end at dam I6.This slope in level is to be seen in Figures 1 and 3. The bubble pipeassembly operates as follows: Air under pressure comes into pipe 68 andis controlled by reducing control valve 47 to a pressure as indicated ongauge 46. Air pressure then flows from the manifold 45 through pipe 41'upwardly through casing M in which there is a known or usual pressureleveling apparatus. From this casing, the air-pressure passes throughvalve 63, casing G2 and downwardly through coiled pipe ll into thebubble pipe 34, from which air is emitted through elbow and nipple 36into the high level stock. From manifold 45, air pressure also flowsthrough horizontal pipe 59 through casing 50, that is equivalent tocasing M,

through valve 50' to and through U-shaped casing 42, down coiled pipe 49into bubble pipe 35, from which air is emitted through elbow and nipple36 into the lower level stock. The same degree of air pressure is thussupplied to both bubble pipes 34 and 35, but since pipe 36 has a higherback pressure in it, than pipe 35, the pressure pipes 53 1eading fromcasing 44 and 55 leading from casing 50 have diiferential pressures inthem. This differential pressure between the pipes causes the instrument55 to act when their relative difference becomes too great, or passes adanger factor, whereupon the instrument permits air pressure to flowthrough line 51 to the d luting water valve control 33. This valve remains open until the relative differential pressures between pipes 53and 55 decrease to within the allowance permitted, whereupon thediluting water valve is operated to reduce the volume of diluting waterbeing added, or perhaps is completely closed. Thus undue fluctuations inrelative back pressure diiierential exerted on the bubble-pipes 3t and35 due to change in the slope of the fluid level of the stock flowing inthe control station, bring about more or less diluting .,to theslightest change in consistency.

water to be added to the stock through the water The horizontal zone ofemission of air by the nipp1es'36' of the bubble pipes permit ofadjustment relatively. That is, they 'can be in the same horizontalplane as shown in Fig. 7, or one can be adjusted to be higher than theother, as some peculiar or unusual stock conditions might require. Thecoils in the pipes 41 and 49 allow for vertical adjustment of the bubblepipes without interfering with the airlines connected to them. This canbe accomplished by having the nipples 36 pass through a plate 10 that isfastened to the nipple and arranged to slide vertically in groovedflanges 1| provided on the inner faces of the casing sides 39, wherebythere is established a iace-to-iace relationship between the plate 10and the inner face of a respective side wall portion of the casing 39.

Occasionally the bubble pipes 34 and 35 may oecome clogged or encrusted,so a water flushing arrangement has been provided for them which isoperable by shutting off valves 48 and 50' followed by turning on valve52 which permits water from the pipe-line ii to flow downwardly throughthe casing 42 and then downwardly through pipes 4| and 49 to and throughbubbles pipes II and 35 respectively, to flush from them anyaccumulations v therein.

A control tank that has proven satisfactory had as inside measurementsan overall length of 6-2%", a width of 27%", and a depth of 36". Theinlet and overflow compartments were about 13" square, while themidfeather was 4'-0 long.

Among the advantages realizable. from the practice of this inventionare: Manually initiated changes of consistency'can be easily made byturning the knob on the control or regulator instrument 54 which changesthe relative position of the valve opening, admitting more or less waterto the stock stream and reducing or increasing consistency. As themeasuring system is not required to do any oi.' .the mechanical work ofcontrolling the valve, light parts can be used in the control,eliminating inertia. Hunting of the valve is eliminated as it respondsinstantly The recording of consistency before and after regulation, on atwenty-four hour or more chart, is a distinct advantage, especially forchecking irregularities in stock consistency during preparation orhandling from heaters to stuff-chest, for if the consistency of thestock in the chest is beyond the range of the control, it shows on thechart and the reason for the unsatisfactory operation can beinvestigated. This control apparatus has proved that it can maintainconsistency within plus or minus 1/10 of 1% provided the stock isdelivered to the control station at consistencies between 2 and 7%.

We claim:

1. A control station for regulating the consistency of a supply of fluidstock by regulating the dilution thereof, comprising a flow channel forthe stock, said flow channel having a vertical wall portion both sidesof which are adapted to be exposed to the flow of the stock beingregulated, as the stock flows first past one and then past the otherside, said vertical wall portion having a recess, a consistency controldevice adapted to be disposed in said recess, and comprising a baseconstruction mounted on said vertical wall portion, a pair of airpressure bubble pipes mounted on said base construction and extending insaid recess,fsaid bubble pipes having lower end air releasing openingsdisposed so that the plane of each opening substantially registers witha respective side face of said wall portion, an air pressure supplyconnection, a branch connection between said air pressure supplyconnection and each bubble pipe, and a pressure throttling deviceinterposed in each branch connection.

2. A control station according to claim 1, with the addition of meansfor blanking ofl. said recess, to substantially restore the respectiveexposed surfaces of said wall portion, that are interrupted by saidrecess.

3. A control station according to claim 1, with addition of means forblanking 011 said recess, to substantially restore the respectiveexposed surfaces of said wall portion, that are interrupted by saidrecess, said blanking oif means comprising a box-like constructionmounted in said recess and adapted to house said bubble pipes, andprovided with side wall openings substantially registering withthe-openings of said bubble pipes.

4. A control station according to claim 1, with the addition of meansfor blanking off said recess, to substantially restore the respectiveexposed surfaces of said wall portion, that are -in-.

terrupted by said recess, said blanking of! means comprising a box-likeconstruction mounted in said recess and provided with openings larger,than those of the lower end openings of said bubble pipes, and avertical plate member fixed terminal portion thereof, each plate memberhaving i'ace-to-face relationship with the inner face of a correspondingside wall portion of said box-- like construction, said plate membersbeing eifective to blank off the diflerential of area between the lowerend opening of the associated bubble pipe and the corresponding largeropening in the box-like construction.

5. A control station according to claim 1, with the addition ofme'ansfor blanking of! said recess, to substantially restore the respectiveexposed surfaces of said wall portion, that areinterrupted by saidrecess, said blanking off means comprising a box-like constructionmounted in said recess with openings larger than those of the lower endopenings of said bubble pipes, and a vertical plate member fixed on eachbubble pipe and constituting the lower terminal portion thereof, eachplate member having face-to-face relationship with the inner face of acorrespond ing side wall portion of said box-like construction, saidplate members being effective to blankoif the differential of areabetween the lower end opening of the associated bubble pipe and thecorresponding larger opening in the box-like conon each bubble'pipe andconstituting the lower struction, and means for vertically adjusting theposition of each bubble pipe while said plate members maintain theclosure of said dinerentials of area.

6. A control station according to claim 1, with ,the addition that thepressure throttling devices are also mounted upon said base constructionand unitary therewith.

RICHARD D. KEHQE. CURT

